Semiconductor laser amplifiers are becoming increasingly more important components for optical signal processing applications. In addition to simple loss compensation and switching functions, a semiconductor laser amplifier can provide simultaneous amplification and detection of an optical signal. Recently, amplifiers which exploit this dual capability have demonstrated improved detection capability by employing a split contact and performing the detecting function at the rear contact. See C. Jorgensen et al., "Two-Section Semiconductor Optical Amplifier Used as an Efficient Channel Dropping Node", IEEE Photon. Technol. Letters, Vol. 4, pp. 348-350, 1992.
As photonic integrated circuits with integrated semiconductor laser amplifiers become increasingly complex, it becomes necessary to monitor amplifier gain to perform automatic gain control or to enhance system robustness. This invention is directed toward satisfying this need of monitoring the optical gain of a semiconductor laser amplifier.